1. Field of the Invention
The invention relates to the field of portable lighting that can include hybrid or multiple power sources including photovoltaic panels.
2. Description of the Related Art
A wide variety of portable light sources have been developed to provide portable utility lighting generally for temporary use when the ambient lighting is insufficient for the user's needs. One broad category of such portable lighting devices is generally referred to as flashlights. Flashlights are generally configured for handheld use and include a self-contained power supply such that a user can manipulate the flashlight by hand and direct the emitted light where desired.
The two typical power sources employed in flashlights are either an electrochemical battery source or an electromechanical generator employing the Faraday effect. Battery power sources for flashlights can comprise disposable type battery sources such as alkaline or lithium based batteries and/or rechargeable battery sources such as nickel cadmium and/or nickel metal hydride. Battery power sources offer the advantage of a relatively long useful life, low-cost, ready availability, and a well-understood and developed technology. Battery power sources do have the disadvantage, however that they are subject to passive discharge over time, even if the flashlight is not used. Thus, a user can find that the battery power source has discharged rendering the flashlight unable to provide the desired light. Unfortunately, such discovery of a depleted battery state frequently occurs at the time of need of the auxiliary light.
Flashlights with rechargeable batteries can be configured for extended connection to a grid power source such that the rechargeable batteries are kept in a state of charge. However, such a configuration of flashlights places the limitation on a user that the flashlights remain connected to the power grid to maintain the battery state of charge. This would limit the ability to maintain the rechargeable battery's state of charge should the user wish to keep the flashlight in a location not provided with a connection to the electrical grid, for example in a vehicle.
Electromechanical generating power sources operating on the Faraday effect have the advantage of independence from the electrical grid. A user can provide mechanical work, typically either reciprocating linear “shaking” motion or rotational motion, such as by rotating a hand crank. Such electromechanical generating systems are frequently supplemented by a short-term electrical energy storage element, such as one or more capacitors to reduce the need for the user to continuously provide mechanical work while light output is desired. However, the storage capacity of such auxiliary energy storage elements is often of relatively low capacity such that the user has only a relatively brief period of light output from the auxiliary storage element before additional work energy must be provided to resume light output from the flashlight. Such electromechanical generating systems also suffer the disadvantage that the mechanical work and motion involved can produce wear thereby limiting the useful life of the flashlight. Electromechanical generation is also inconvenient as a user must at least periodically direct their attention and effort to powering the flashlight rather than the task at hand.